A common method for the recovery of oils from plant material is to extract the oils with a solvent suitable for leaching the oils from the plant material. The solvents used during extraction include, but are not limited to, acetone, butane, carbon dioxide, ethanol, hexane, isopropyl alcohol, and propane. Many of the solvents used in extraction have hazardous properties such as flammability, explosive vapors, physiologic damage, and/or asphyxiant properties. These hazards may occur during use of open containers when the solvent evaporates, during solvent spills or leaks, when the spent solvent-wetted plant material is removed from the extraction system, and during venting of solvent from extraction equipment. The equipment and systems used during extraction includes a variety of devices including, but not limited to, leaching vessels, extraction vessels, distillation systems, condensers, cooling and heating baths, pipes, tubing, vacuum pumps, and pressurized gas bottles.
In many countries, regulations and codes are in place to protect persons working with flammable and toxic substances. These regulations and codes often require the use of facilities equipped with explosion-proof electrical equipment, lighting and fixtures; explosion blast venting capabilities, ventilation rated for use with hazardous materials; and monitoring and alarm systems to detect the presence of hazardous conditions. The construction or retrofit of a room in new or existing buildings with hazardous-rated equipment is expensive. Each component or equipment unit may require rating as explosion-proof or intrinsically safe.